Distribution and abundance of young pelagic fish : monitored by hydroacoustics in two coastal areas in the SW Bothnian Sea

• The distribution of young pelagic fish in autumn was studied by hydroacoustic techniques in two coastal areas in the SW Bothnian Sea, one exposed to cooling water from a nuclear power plant and the second a reference area free from local disturbance. Generally, herring young-of-the-year dominated among pelagic fish and often constituted over 80% of the total numbers of fish counted. Young herring were concentrated to certain parts of the studied archipelagos, predominantly to the more shallow waters and to the outer parts of the small inlets commonly occurring in these coastal areas. When comparing the results of subsequent visits in the different study areas, it was evident that the estimated densities often varied markedly between days, although the distributionpatterns did not change. This was interpreted as an effect of migrations in and out of waters too shallow to be monitored by echosounder techniques. In September young herring evidently still depends upon an access to sheltered and very shallow habitats. Abundances of herring fry were higher in the cooling water exposed area compared to the reference, supporting earlier observations on positive temperature effects on fishrecruitment at this nuclear power plant.

Ämnesord

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Oceanografi, hydrologi och vattenresurser (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Oceanography, Hydrology and Water Resources (hsv//eng)

Nyckelord

pelagic fish

herring

hydroacoustics

nuclear power

migration

pelagisk fisk

sill

hydroakustik

kärnkraft

fiskvandring

National

Nationellt finansierad miljöövervakning

Ett rikt växt- och djurliv

A Rich Diversity of Plant and Animal Life

Publikations- och innehållstyp

vet (ämneskategori)

rap (ämneskategori)